The present invention relates to a method and apparatus for joining together a web from a new roll of material to a web from an expiring roll that is being fed to a continuous web processing operation. More particularly, this invention relates to a method and apparatus for joining, by a zero-speed butt splice, the leading end from a new roll of web material to the trailing end from an expiring roll of web material where the web material is continuously processed, at a relatively high speed, through a web processing operation and where the web material, such as the web materials used in making disposable diapers, must be maintained at a relatively constant, relatively low tension because of the nature of the web material.
Disposable diapers are made by combining various webs of materials, one on top of another, in a relatively high speed, continuous manufacturing process. These webs include polyethylene, and various absorbent and hydrophilic inner liners that have different modula of elasticity and that readily inelastically deform under even low tensions. Disposable diaper manufacturing processes are additionally complicated, from a web handling standpoint, by the inclusion of elastic bands that serve, in the completed diaper, to prevent leakage about the infant's legs.
In the past, the webs were typically processed at a rate of around six hundred feet per minute in disposable diaper manufacturing lines. In an effort to further reduce manufacturing costs, it has now been proposed to process the webs at around eight hundred to one thousand feet per minute. Additionally, new web materials utilized in disposable diapers will require that the webs be run at extremely low tensions, for instances, at one-half to one pound total, on a twenty-inch wide web, or at approximately 0.025 pli (pound per linear inch). The total tension must be held within plus or minus one-quarter pound to avoid inelastic deformation of the web materials.
The maintenance of such relatively low tensions and relatively high processing speed is complicated by the fact that a web must be brought to a complete stop each time a splice is made. At the processing speeds contemplated, this stoppage of the web to accomplish a butt splice must occur relatively frequently. No prior apparatus or methods were known that were capable of handling webs within these specifications, and particularly capable of handling webs of materials utilized to manufacture disposable diapers.
SUMMARY OF THE INVENTION
In principal aspect, the present invention relates to an improved method for forming an accurate, zero-speed butt splice or joint and to an improved apparatus suitable for expeditiously performing the method while the webs are being continuously processed, downstream of the splicing apparatus, at relatively high speeds and under relatively constant, relatively low tensions. By using the improved method, a web from a new roll of material may be easily, quickly and accurately joined to a web which is from an expiring roll of material and which continues to be run at relatively high speeds, downstream of the roll, under relatively low tension, along a predetermined path of travel that includes a running web storage means, such as a web storage festoon. While a wide variety of materials may be butt spliced together, the 15 improved method and apparatus of the present invention are especially suited for the splicing of the webs of materials used in the making of disposable diapers. Further, the webs can be run in disposable diaper manufacturing lines at speeds of eight hundred to one thousand feet per minute under tensions of 0.025 pli (that is, one-half to one pounds total) on a twenty inch wide web, while zero-speed splices are being made. Because of the significantly increased manufacturing line speed, these butt splices must be made more frequently, and the improved method and apparatus have been able to save a number of diapers per splice that would have otherwise had to be discarded using heretofore conventional splicing apparatus.
The improved method and apparatus of the present invention afford a number of other important commercial advantages. Minimum operator involvement is required to run the apparatus of the present invention, and thus accomplish a good quality butt splice. As noted, the improved methods and apparatus may utilize a zero-speed splicing concept, that is, the expiring or old web is brought to a stop during the actual splicing of the new web to the expiring web. Nevertheless, due to the short time required to form the butt splice and the use of the running web storage means, the web processing operation can continue at relatively high speeds as material is drawn from the running web storage means during the splicing operation. Thus, the use of the improved method and apparatus enable significantly increased production to be achieved in terms of the overall speed of the disposable diaper manufacturing line.
Accordingly, it is an object of the present invention to provide an improved method for forming a good quality butt splice by holding a portion of the web from the new roll against an anvil that includes a cutting edge disposed at an angle to the path of travel of the expiring web running past the anvil. The portion of the new web is then trimmed or cut along the cutting edge of the anvil so that the trimmed edge of the downstream, leading end of the new web is aligned with and conforms to the anvil's cutting edge. Single-sided adhesive tape is then applied to the leading trimmed end so that a portion of the tape extends downstream beyond the anvil's cutting edge and the trimmed end of the new web. The web from the expiring roll is then momentarily stopped, a portion of that web is held against the anvil; that portion of the expiring web is trimmed or cut along the anvil's cutting edge, and the trailing end of the expiring web is pressed against and adhered to the downstream portion of the tape so that the leading end of the new web and trailing end of the expiring web are secured or joined together by the tape. The joined new and expiring webs are then permitted to run again through the running web storage means and to the web processing operation such as in a disposable diaper manufacturing line.
Another object of the present invention is to provide an improved method, as described, where the portion of the expiring web is trimmed and the trailing end is adhered to the downstream portion of the tape substantially simultaneously. A related object is to provide an improved method, as described, where the leading end of the new web and the downstream portion of the tape are supported during the time the portion of the expiring web is trimmed and its trailing end is pressed against and adhered to the downstream portion of the tape.
A further object of the present invention is to provide an improved method for forming a butt splice, as described, between the trailing end of an expiring roll and the leading end of a new roll of web materials used in the manufacture of disposable diapers, where the diameter of the expiring roll is calculated; where a splice is initiated when the roll diameter has run down to a preselected limit; where the expiring roll is stopped and the expiring web is clamped adjacent to the anvil upon initiation of the splice; where the portion of the expiring web is cut along the anvil's cutting edge, a part at a time, across the expiring web and beginning at one side edge thereof, so that the point of cutting moves across the portion of the expiring web from one side edge to the other side edge, so that the uncut part of the portion of the expiring web remains under tension ahead of the point of cutting and so that the cut part of the portion of the expiring web, behind the point of cutting, is adhered to the adhesive tape on the leading end of the web of the new roll substantially simultaneously as the point of cutting moves across the portion of the expiring web; where the new web is unclamped and the new roll is quickly driven up to line speed upon completion of the cutting of the expiring web; and where the web speed is maintained at line speed as and after the festoon has been restored to its normal position. A related object is to provide an improved method, as described, for forming butt splices for webs of materials used in the manufacture of disposable diapers where the webs must be processed at relatively high speeds and under relatively constant, relatively low tensions in a disposable diaper manufacturing line.
A still further object of the present invention is to provide an improved apparatus that is suitable for performing the improved method as described and that can expeditiously form a good quality butt splice by trimming or cutting both the new and expiring webs along the same anvil cutting edge and by trimming the expiring web while simultaneously adhering the trimmed trailing edge of the expiring web to adhesive tape projecting downstream from the leading end of the new web. A related object of the present invention is to provide an improved apparatus as described, where the web need only be momentarily stopped, adjacent to the apparatus, to effect the formation of a good quality butt splice and so that through the use of a running web storage means, the remainder of the web can continue running uninterruptedly through the web processing operation during the entire splicing operation.
These and still other objects, advantages and aspects of the present invention are more fully set forth in the following detailed description of the preferred embodiment of the present invention.